AFAIK, the only official documentation from Microsoft to build a managed satellite dll for a XML add-in is the following gem in MSDN, that involves using command-line tools such as resgen.exe (Resource File Generator) or al.exe (Assembly Linker) and Windows tools such as Notepad:

Of course there is a much better way to create a resource dll that doesn’t involve command-line tools, that is, a class library project in the same solution of the add-in that provides the resources. I have updated the following article to cover this scenario: